EP0374956A2 - Zerstörbare Form - Google Patents

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Publication number
EP0374956A2
EP0374956A2 EP89123816A EP89123816A EP0374956A2 EP 0374956 A2 EP0374956 A2 EP 0374956A2 EP 89123816 A EP89123816 A EP 89123816A EP 89123816 A EP89123816 A EP 89123816A EP 0374956 A2 EP0374956 A2 EP 0374956A2
Authority
EP
European Patent Office
Prior art keywords
mold
decay
powder
binder
molding
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89123816A
Other languages
English (en)
French (fr)
Other versions
EP0374956A3 (de
Inventor
Hiroaki C/O Nkk Corporation Nishio
Tatsuhito Nkk Corporation Takahashi
Kazuya Nkk Corporation Yabuta
Akira Nkk Corporation Kato
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
JFE Engineering Corp
Original Assignee
NKK Corp
Nippon Kokan Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP32217788A external-priority patent/JPH02169145A/ja
Priority claimed from JP32217888A external-priority patent/JPH02169204A/ja
Priority claimed from JP32217688A external-priority patent/JPH02169144A/ja
Application filed by NKK Corp, Nippon Kokan Ltd filed Critical NKK Corp
Publication of EP0374956A2 publication Critical patent/EP0374956A2/de
Publication of EP0374956A3 publication Critical patent/EP0374956A3/de
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B7/00—Moulds; Cores; Mandrels
    • B28B7/34—Moulds, cores, or mandrels of special material, e.g. destructible materials
    • B28B7/342—Moulds, cores, or mandrels of special material, e.g. destructible materials which are at least partially destroyed, e.g. broken, molten, before demoulding; Moulding surfaces or spaces shaped by, or in, the ground, or sand or soil, whether bound or not; Cores consisting at least mainly of sand or soil, whether bound or not

Definitions

  • This invention relates to molds for molding powder and then sintering it to produce a product of ceramic, sintered metal or the like.
  • the powder is molded into a prescribed form by filling it into a metal mold followed by pressuring, or by suspending it into solvent together with a binder such as water followed by casting into a porous mold, or by kneading it together with resin followed by injecting into a metal mold.
  • a binder such as water
  • the molded body of the powder is separated from the mold prior to the sintering process.
  • the mold has a separable structure so as to demold the molded body without damage.
  • the shell mold used for the precision molding should be excellent in heat resistance, thermal shock, and strength, because a molten metal is poured therein.
  • the molded body formed of powder keeps its form by entaglement of the powder particles theirselves or by binding the powder particles through resin, inorganic binder or the like. Therefore, the strength of the molded body is very weak compared with the shell mold used for precision molding of metal. Thus, it is considered to be difficult to remove the shell mold from the molded body of powder without damage, and the shell mold has never been utilized therefor.
  • An object of the invention is to provide a decay mold capable of molding powder without damaging the molded body irrespective of its form.
  • Another object of the invention is to provide a decay mold capable of molding powder without dividing the mold into several pieces irrespective of its form and thereby capable of improving the reliability of the sintered body and the simplicity of the manufacturing process.
  • the present invention provides decay molds achieved the above objects, and are characterized by destroying decomposing or dissolving the shell mold utilizing the volume change occuring at a transition, thermal decomposition or dissolution of the mold without damaging the molded body.
  • a decay mold of the invention comprises a powder material having a transition accompanied with a volume change occurring at a temperature lower than the sintering temperature and a binder thereof.
  • Another decay mold of the invention comprises a material thermally decomposable at a temperature lower than the sintering temperature.
  • Another decay mold of the invention comprises a material soluble at least in one solvent in which the molding assistant to impart formability to the powder to be molded is insoluble.
  • the powder material When the decay mold is comprised of the powder material having the transition, the powder material must be transformable, and the transition must be accompanied with a volume change. The volume change may be either of expansion or contraction.
  • the transition temperature of the powder material must be lower than the sintering temperature of the molded body.
  • the transition temperature When the molded body of the powder sintering is calcined, the transition temperature is preferably lower than the calcination temperature.
  • the transition temperature is higher than the sintering temperature, the molded body is necessary to be heated higher than the sintering temperature in order to occur the transition resulting to break the molded body.
  • a preferred particle size is 1 to 100 ⁇ m.
  • Suitable powder materials include zirconia, fused silica and zircon sand, zirconia is transformed with volume expansion in the vicinity of 1100°C, and fused silica is transformed with volume shrinkage into cristobalite at higher than 1100°C.
  • the binder binds the powder material to keep the molded form.
  • a preferred binding strength of the powder material is destroyed readily by the volume change caused by the transition.
  • Suitable binders include alumina sol, silica sol and zirconia sol.
  • the above decay mold may contain other materials than the powder material and the binder, such as alumina powder, silicon nitride powder, silicon carbide powder and mullite powder.
  • composition of the above mold a suitable content of the powder material is 30 to 90 wt. %, that of the binder is 10 to 30 wt. % and that of the other materials is less than 50 wt. %.
  • the product of the thermal decomposition is preferably vapor or small pieces of solid matter at the temperature of the thermal decomposition in view of facilitating the removal of the destroyed mold.
  • the thermal decomposition temperature must be a temperature not to damage the sintering material.
  • the thermal decomposition temperature is preferably for the mold to resist at least up to the initial stage of the calcination.
  • the thermally decomposable material may be the material or a principal component of the mold, or a binder to bind the material forming the mold.
  • Suitable materials for the former case include gypsum and various resins. Gypsum decomposes in the vicinity of 300°C to produce gypsum anhydride and water, and further decomposes about 900°C.
  • the resin may be thermoplastic resin or thermosetting resin.
  • the resin may be porous.
  • Various resins are commercialized, and the thermal decomposition temperature widely distributes from about 100° C to about 500°C. Therefore, a suitable resin can be selected from commercial resins according to the desired thermal decomposition temperature or the like. Preferred resins are not to evolve harmful gas such as HCl or HCN by the thermal decomposition.
  • the thermally decomposable material when used for the binder, it may be selected from gysum and various resins.
  • the material forming the mold is sufficient to be small pieces destroyed by the thermal decomposition of the mold, and it may be powder, granules, rods, fiber or the like.
  • the material forming the mold are ceramic powders such as alumina and titania and metal powders.
  • the above decay mold may be formed of the thermally decomposable material or a mixture of the thermally decomposable material and the material forming the mold alone, or may contain other components.
  • a suitable content of the thermally decomposable material is more than 20 wt. %, preferably 35 to 80 wt %, a suitable content of the material forming the mold is more than 20 wt. %, preferably 35 to 60 wt. %, and a suitable content of other components is less than 10 wt. %.
  • the solvent may be water, alcohol, acetone, ether, benzene, toluene, hexane or the like.
  • the solubility of the soluble material is preferably great.
  • the solvent should be not to dissolve the binder.
  • the soluble material should be insoluble at least in one solvent capable of dissolving the pattern, but should be soluble at least in one of the other solvents. In general, most of patterns are formed of paraffin.
  • the soluble material is insoluble at least in one solvent capable of dissolving paraffin such as hexane, but is soluble at least one solvent other than the above solvent such as water.
  • the solubility of the pattern is not necessary to be considered.
  • the soluble materials are water-soluble urea resin, ethyl cellulose, methyl cellulose, polyvinyl butyral, polyvinyl alcohol and the like.
  • the soluble material may be the material of the mold or a principal component thereof or a binder to bind the material forming the mold.
  • the material forming the mold is sufficient to be small pieces destroyed by dissolving the soluble material, and it may be powder, granules, rods, fiber or the like.
  • the material forming the mold are ceramic powders such as alumina and titania, metal powders, paper, yarn and the like.
  • the above decay mold may be formed of the soluble material or a mixture of the soluble material and the material forming the mold alone, or may contain other components.
  • a suitable content of the soluble material is more than 10 wt. %, preferably 20 to 70 wt. %, a suitable content of the material forming the mold is more than 10 wt. %, preferably 40 to 80 wt. %, and a suitable content of other components is less than 20 wt. %.
  • a slurry containing the powder material and the binder, a slurry or solution of the thermally decomposable material or the soluble material are prepared.
  • the slurry or the solution is applied to a pattern followed by drying.
  • the mold can be completed by repeating the application and the drying.
  • the application may be conducted by immersing or spraying as well as brushing.
  • the solvent of the slurry or the solution may be water, methanol, ethanol, acetone, ether, hexane, toluene, benzene or the like.
  • a suitable concentration of solid materials in sum of the powder material and the binder is 30 to 80 wt.
  • thermoplastic resins they may be melted and then applied to the pattern. After the mold is formed, the pattern is removed by a suitable means such as dissolving using a suitable solvent or melting.
  • a sintered article can be produced using the mold of the invention by filling the raw powder for sintering in the mold by casting, injection molding, vibrational compression molding or the like, followed by calcination, if necessary. Subsequently, in the case of the mold comprised of the powder material having the transition, the mold is heated up to higher than the transition temperature of the powder material, and the mold is allowed to decay by the volume change caused by the transition. When the transition temperature is near the calcination temperature, the decay of the mold also proceeds during the calcination. The transition may be conducted twice or more times by lowering the temperature to the original state, then heating the mold again, or the like.
  • the mold is heated up to higher than the thermal decomposition temperature of the thermally decomposable material, and the mold is allowed to decay or disappear by the thermal decomposition.
  • the thermal decomposition temperature is near or lower than the calcination temperature, the decay or disappearance of the mold also proceeds during the calcination.
  • the mold can be allowed to decay or dissolve by adding a solvent capable of dissolving it. The destroyed mold is removed, and the molded body is sintered to obtain a sintered product.
  • the molded body may be sintered in the state placed in the mold. In this case, the mold decays during sintering, and can be removed after the sintering.
  • the mold of the invention Since a part or the whole of the mold of the invention is constructed by a material of which the principal component has a transition accompanied with a volume change, or it is thermally decomposable, or it is soluble in a solvent, the mold decays or disappears by the volume change due to the transition, when the mold is heated to higher than the transition temperature or cooled to lower than the transition temperature or heated to higher than the decomposition temperature or immersed in the solvent.
  • the mold of the invention makes possible an integral molding of an article having a complex structure which was formed by molding divided into several parts followed by joining them. Thereby, the reliability of the sintered product is sharply improved, and the manufacturing process of the molded body can be simplicated.
  • a pattern of the curved pipe shown in Figure 1 was prepared according to the pattern-making process used in the shell molding of precision casting.
  • ZrO2 was supended in a commercial aqueous alumina sol in a concentration of 70 wt. %.
  • the above pattern was immersed in the ZrO2 suspension, and then, it was taken out followed by drying. This operation was repeated 5 times in total.
  • the pattern coated with ZrO2-alumina sol was heated to about 200°C, and the pattern was removed by melting to obtain a shell mold. Ceramic powder was molded by injection molding using this mold, and dewaxed by heating to about 600°C.
  • the mold was destroyed by heating to 1100 C in an oven to obtain a molded body of the ceramic powder in a form of the curved pipe without damage.
  • the molded body was sintered under usual conditions.
  • a test piece cut off the sintered body had a similar strength to a test piece cut off another sintered body obtained by molding through a CIP process and sintering under the same conditions.
  • a shell mold was prepared in the same manner as Example 1, except that fused silica was suspended in a concentration of 65 wt. % instead of 70 wt. % of ZrO2, and the pattern was immersed 7 times in the suspension.
  • a ceramic sintered body was prepared in the same manner as Example 1, except the mold was destroyed by cooling from 1200°C to room temperature. The molded body was obtained without damage, and a test piece cut off the sintered body had a similar strength to a test piece cut off another sintered body obtained by molding through a CIP process and sintering under the same conditions.
  • a shell mold was prepared in the same manner as Example 1, except that the ZrO2 suspension was relaced by a 70 wt. % commercial gypsum suspension. Ceramic powder was molded by cast molding using this mold, and dewaxed by heating to about 600°C. Most of the mold was fallen and the remaining part adhered to the molded body was destroyed by blowing using compressed air to obtain a molded body of the ceramic powder in a form of the curved pipe without damage. The molded body was sintered under usual conditions. A test piece cut off the sintered body had a similar strength to a test piece cut off another sintered body obtained by molding through a CIP process and sintering under the same conditions.
  • a pattern of the curved pipe shown in Figure 1 was prepared according to the water-soluble pattern-making process used in the shell molding of precision casting.
  • polyethylene was melted by heating at about 200 C.
  • the above pattern was immersed in the polyethylene liquid, and then, it was taken out followed by drying. This operation was repeated 3 times in total.
  • the pattern coated with polyethylene was immersed in water heated to a suitable temperature for the dissolution of the pattern, and the pattern was removed by dissolving to obtain a shell mold.
  • Ceramic powder was molded by injection molding using this mold, and dewaxed by heating to about 600 C.
  • the shell mold was decomposed together with the forming assistant during dewaxing to obtain a molded body of the ceramic powder in a form of the curved pipe without damage.
  • the molded body was sintered under usual conditions.
  • a test piece cut off the sintered body had a similar strength to a test piece cut off another sintered body obtained by molding through a CIP process and sintering under the same conditions.
  • a paraffin pattern of the curved pipe shown in Figure 1 was prepared according to the pattern-making process used in the shell molding of precision casting.
  • water-soluble urea resin was dissolved in water in a concentration of 50 wt. %.
  • the above pattern was immersed in the urea resin solution, and then, it was taken out followed by drying. This operation was repeated 10 times in total.
  • the pattern coated with urea resin was immersed in hexane which can dissolve the paraffin but cannot dissolve the urea resin to remove the pattern.
  • Ceramic powder was molded by low pressure injection molding, and immersed in water together with the mold. Thus, the shell mold was removed by dissolving to obtain a molded body of the ceramic powder in a form of the curved pipe without damage.
  • the molded body was sintered under usual conditions.
  • a test piece cut off the sintered body had a similar strength to a test piece cut off another sintered body obtained by molding through a CIP process and sintering under the same conditions.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Mold Materials And Core Materials (AREA)
  • Compositions Of Oxide Ceramics (AREA)
EP19890123816 1988-12-22 1989-12-22 Zerstörbare Form Withdrawn EP0374956A3 (de)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP32217788A JPH02169145A (ja) 1988-12-22 1988-12-22 崩壊性鋳型
JP322176/88 1988-12-22
JP32217888A JPH02169204A (ja) 1988-12-22 1988-12-22 崩壊性鋳型
JP322177/88 1988-12-22
JP32217688A JPH02169144A (ja) 1988-12-22 1988-12-22 崩壊性鋳型
JP322178/88 1988-12-22

Publications (2)

Publication Number Publication Date
EP0374956A2 true EP0374956A2 (de) 1990-06-27
EP0374956A3 EP0374956A3 (de) 1991-04-24

Family

ID=27339895

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19890123816 Withdrawn EP0374956A3 (de) 1988-12-22 1989-12-22 Zerstörbare Form

Country Status (1)

Country Link
EP (1) EP0374956A3 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0473383A2 (de) * 1990-08-27 1992-03-04 Cca Inc. Verfahren zur Herstellung von gemusterten geformten Gegenständen
EP0479512A2 (de) * 1990-10-01 1992-04-08 Cca Inc. Verfahren zur Herstellung eines gemusterten Formkörpers
US5445772A (en) * 1991-05-23 1995-08-29 Cca Inc. Method of producing patterned shaped article

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3123886A (en) * 1964-03-10 Assembly fom forming refractory tubes
GB2030065A (en) * 1978-09-18 1980-04-02 Norton Co Slip casting
US4271114A (en) * 1977-07-14 1981-06-02 General Electric Company Method of compacting dry powder into shapes
GB2107635A (en) * 1978-09-18 1983-05-05 Norton Co Process of forming a refractory shape using slip casting
DE3511694A1 (de) * 1984-04-02 1985-10-10 Hitachi, Ltd., Tokio/Tokyo Schlickergiessformverfahren und schlickergiessform
EP0243502A1 (de) * 1985-10-21 1987-11-04 Kouransha Kabushiki Kaisha Giessform zum giessen von pulver in plakettenform
EP0288236A2 (de) * 1987-04-20 1988-10-26 Hitachi, Ltd. Verfahren zur Herstellung eines bei hohen Temperaturen supraleitendes Material

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3123886A (en) * 1964-03-10 Assembly fom forming refractory tubes
US4271114A (en) * 1977-07-14 1981-06-02 General Electric Company Method of compacting dry powder into shapes
GB2030065A (en) * 1978-09-18 1980-04-02 Norton Co Slip casting
GB2107635A (en) * 1978-09-18 1983-05-05 Norton Co Process of forming a refractory shape using slip casting
DE3511694A1 (de) * 1984-04-02 1985-10-10 Hitachi, Ltd., Tokio/Tokyo Schlickergiessformverfahren und schlickergiessform
EP0243502A1 (de) * 1985-10-21 1987-11-04 Kouransha Kabushiki Kaisha Giessform zum giessen von pulver in plakettenform
EP0288236A2 (de) * 1987-04-20 1988-10-26 Hitachi, Ltd. Verfahren zur Herstellung eines bei hohen Temperaturen supraleitendes Material

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0473383A2 (de) * 1990-08-27 1992-03-04 Cca Inc. Verfahren zur Herstellung von gemusterten geformten Gegenständen
EP0473383A3 (en) * 1990-08-27 1992-08-26 Cca Inc. Method of producing patterned shaped article
US5376321A (en) * 1990-08-27 1994-12-27 Cca Inc. Method of producing patterned shaped article
EP0479512A2 (de) * 1990-10-01 1992-04-08 Cca Inc. Verfahren zur Herstellung eines gemusterten Formkörpers
EP0479512A3 (en) * 1990-10-01 1992-09-02 Cca Inc. Method of producing patterned shaped article
US5368791A (en) * 1990-10-01 1994-11-29 Cca Inc. Method of producing patterned shaped article
US5445772A (en) * 1991-05-23 1995-08-29 Cca Inc. Method of producing patterned shaped article

Also Published As

Publication number Publication date
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